Delivery of active agents across the skin or mucosal membrane is convenient, pain-free, non-invasive and circumvents problems associated with the “first pass effect”. Such transdermal or topical drug delivery is typically restricted to low molecular weight drugs and drugs with specific lipophilic/hydrophilic balance able to penetrate the stratum corneum.
Transdermal drug delivery systems enable chemical modification of the barrier properties of the skin to effectively and efficiently permit permeation thereof. Known drawbacks of transdermal delivery systems are, for example, the length of time needed for permeation, a frequent dosing regimen, and the volume size of a transdermal composition needed to transdermally deliver a sufficient therapeutic amount of the active agent.
Diclofenac (2-(2,6-dichloranilino) phenylacetic acid) is a non-steroidal anti-inflammatory drug (NSAID) used to reduce inflammation and, as an analgesic, to reduce pain. It is available in sodium, potassium, epolamine or diethylamine salt form in numerous dosage forms (oral tablet, oral syrup, topical gel, cataplasm, ophthalmic drop, suppository, etc.).
An example of a well-known transdermal diclofenac formulation is Voltaren® Gel 1% which comprises 1% diclofenac sodium. Voltaren® is indicated in the USA for the relief of the pain due to osteoarthritis of joints amenable to topical treatment, such as the knees and the hands. Up to 4 g of Voltaren® gel can be applied to lower extremities (including the knees, the ankles, and the feet) 4 times daily so that up to not more than 16 g daily of Voltaren® Gel 1% is applied to any single joint of the lower extremities. Up to 2 g of Voltaren® Gel 1% can also be applied to the upper extremities (which include the elbows, the wrists and the hands) 4 times daily so that up to not more than 8 g daily of Voltaren® Gel 1% is applied to any single joint of the upper extremities. Overall, the total dose of Voltaren® Gel 1% should not exceed 32 g per day over all affected joints. Neither the total amount (up to 32 g per day) nor the frequency of application (4 times a day) are satisfactory from a patient perspective.
U.S. Pat. No. 7,335,379 discloses formulations for transdermal or transmucosal administration of active agents, such as diclofenac, containing an alkanol, a polyalcohol, a monoalkyl ether of diethylene glycol and a fatty alcohol with a fatty alcohol content of up to 2%.